[NTG-context] Clipping again

David Arnold dwarnold45 at cox.net
Sun Jun 25 21:58:22 CEST 2006

```Mojca,

Good question of course.

However, I am using this for intermediate algebra students so the
graphs will be lines, absolute value, quadratics, polynomials,
rational functions, radical functions, exponential and logarithmic
functions.

In each case, I would adjust the window to see all important behavior
of the function, extrema, etc. So, for example, if I needed to draw
y=12-x^2, I would not clip this to the boundary (-10,-10)--(10,-10)--
(10,10)--(-10,10)--cycle, because that would chop off the top of the
parabola, and if I added arrows, it would look like I had two
branches. Rather, I might clip y=12-x^2 to the boundary (-10,-20)--
(10,-20)--(10,20)--(-10,20)--cycle in order to see the "turning
point" of the parabola.

That is, I would choose a boundary that would present arrow heads at
each end of the curve. In the case of rational functions, I would
clip each branch separately.

I hope this answers the question.

Thanks.

On Jun 25, 2006, at 12:37 PM, Mojca Miklavec wrote:

> On 6/25/06, David Arnold wrote:
>> Unfortunately, even though this works, mathematicians really want
>> arrows at each end of the graph. Easy enough to do with drawdblarrow
>> P withcolor blue, but the arrows then get clipped. What I really need
>> is to adapt the code below so that my function is clipped to the
>> boundary box, but then redrawn with arrows at each end of it. If
>> anyone can adjust my code to do that, it would be much appreciated,
>> and it would break down a barrier I've faced for years with metapost
>> coding.
>
> Just for clarification: What would you do with a "mexican hat"
> (x^4-4*x^2+4, y between 0 and 3) it if would cut the boundary 4 times?
> Use 4 arrows or just the two at the end?
>
> Mojca
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```